Winston Churchill announces to the British Parliament that they have liberated France, removing any attempt for the Nazis to use it as a staging ground to attack Britain anymore and announce that the Blitzkrieg from the Luftwaffe was officially over. No sooner is this announcement made that a number of Nazi fighter planes appear over London and begin bombing. When R.A.F. fighters attempt to counter attack the Nazis flee and are lost somewhere over Ireland. Overhearing the accounts via radio, the Sub-Mariner decides to swim to England to lend a hand. Meeting with the head of the British secret service, Namor learns that British intelligence does not suspect the Irish of helping out the Nazis, but Namor is implored to investigate Dublin for them.

Taking on a disguise, the Sub-Mariner finds an interesting story in a Dublin newspaper about a local woman who has been arrested for disturbing the peace and claiming that there were banshees on her property. Paying the old woman's bail, Namor has her lead him to the site where she supposedly heard banshees. Investigating the rocks near the water off her property, they find the body of a man wearing clothing that was once worn by the ancient Druids who lived in the area. Examining the body, Namor finds a map leading to a place called "Rockhenge", and is suddenly attacked by a group of men. The old woman is gunned down and Namor is shot in the head. The bullet doesn't kill him, but knocks him out. Thinking him dead, the men take all evidence of the secret Nazi airfield and leave the scene.

When Namor revives, he goes back to the British Secret Service and explains to its head what he saw. When he asks what Rockhenge is, he is told that it is an ancient Druid ritual ground and the two men decide to go and investigate it further. Searching the site, Namor finds an ancient inscription that tells of a massive flood that forced the Druids of Black Moors, their society would build an underwater home to live in. Searching for a passage to this secret realm, Namor finds the secret door but it opens so quickly it crushes his friend from the Secret Service to death. With the mystery thickening, Namor goes into the tunnel to see where it leads, as he does the door behind him closes.

Finding a pool of water, Namor dives in and follows an underwater tunnel into the realm of the Black Moor Druids. Upon surfacing again he is grabbed by the Druids. Considered an enemy of their domain, the Druids take Namor to a chopping block where their youthful leader Cestis plans on smashing Namor's head with a mace. He is stopped by his ally, the Nazi commander Mueller. Recognizing Namor for who he is, he wonders how he found their hideout and orders him to be taken to the "Room of 1000 Questions". Longing to see what this room contains, Cestis follows behind to secretly get a glimpse of it. This room turns out to be a torture chamber where the Nazis intend to get Namor to talk by torturing him with a Swastika shaped branding iron. Breaking free, Namor knocks out all the Nazis on site and finds diving equipment and an airlock in this room.

Going out the airlock he finds a number of domed cities where the Druids toil over the soil to try and keep up with maintaining the heavy demand their Nazi allies are making on their supplies. Searching further, Namor finds an underwater U-Boat dock and the Nazis' secret air field that deploys planes within the Druids' land. Before Namor can escape and warn the British, someone sneaks up behind him and strikes him over the head with a hammer.

Namor has been ambushed by a Nazi soldier who has knocked the Sub-Mariner out with a hammer blow to the head. However, before Namor can be taken prisoner again this Nazi is knocked by Cestis and some of the other Druids who take Namor away to one of their underground chambers. When Namor revives, Cestis tells the Sub-Mariner that they are no longer allied with the Nazis as their union has been akin to slavery. Cestis explains that his people fled the surface world centuries to live in peace and that they welcomed the Germans with open arms until they realized that they were nothing more than warmongers. With no weapons to defend themselves the Druids are at a loss as to what to do, however Namor has a plan. They are unaware that they are being watched by Mueller who floods their room and lets loose a giant octopus to eliminate them.

While the Druids drown, Namor is alone against the powerful octopus but manages to kill the creature. Unable to see the outcome of the battle due to the ink excreted by the octopus, Mueller orders the room drained thinking that Namor must have died. This proves to be a mistake as Namor has survived his encounter with the octopus and beats Mueller and his guards into submission again. Attempting to escape to warn the British, Namor is stopped when Mueller orders his Luftwaffe to blast him out of the water. However attempts to capture the Sub-Mariner fail and Mueller presumes that the hero has escaped to warn the British. Mueller flies to Britain and posing as a British R.A.F. commander tells the local Air Raid Warden that there is a Sub-Mariner impostor in the area.

When Namor attempts to warn the British, he is arrested and brought before the head of the British Secret Service. Noticing there is something wrong with the head, Namor asks for a last cigarette, knowing his friend lights his matches with his thumb nail. When the man posing as the head of British security strikes the match on his shoe, Namor is convinced that he is a spy and punches him out, revealing his disguise. Namor frees the real head of the Secret Service and they capture Mueller. Namor then has the head agree to give him TNT to bring to the Druids to help them remove the Nazis from their home. When Mueller is being brought out to be executed for his crimes, he ingests a powder that turns his body into a human flare that goes off when he dies. This is a signal flair ordering his minions back in the Druids home to launch a full scale assault on Britain.

However, before the Nazis can succeed, Namor mobilizes the Druids and assists them in a revolt that sees the destruction of the Nazi U-Boat base and air-field ending their threat. With the Druids free of their Nazi controllers, they thank Namor for his assistance and tell him that they are relocating their home seven miles further away from shore to keep interlopers from taking control of their people again.

One night, Bill Gunther, the publisher of "Anti-Nazi Comics" is murdered by a mysterious figure who leaves a cartoon warning that the scriptwriter for the comic will be murdered next, using Bill's own blood as ink. This murder piques the interest of the Angel who decides to catch the killer. Over at Anti-Nazi Comics, operations are taken over by Bill's brother Jerry. Their head writer Howards refuses to write any anti-Nazi stories. When the new publisher attempts to hire a writer to take over, nobody wants to take the job. The Angel walks into the office and upon hearing that they are looking for a writer to continue the series takes up the job himself hoping to catch the killer in the act.

The Angel almost blows his cover when he unbuttons his shirt when it's too hot in the office revealing his costume to one of his co-workers but manages to cover up by saying it is a tattoo. That night after the next issue is done, the Angel enters the elevator with his colleagues when someone shuts off the light and attempts to stab him. The Angel manages to avoid getting killed and when the light turn back on he suspects Mr. Roberts the artist of being the killer. Roberts denies it, and the Angel takes the killer's knife to examine it later.

On the streets the Angel changes into his costume and begins to follow Roberts. Noticing that he is being tailed, Roberts manages to get the drop on the Angel and knock him out. Rushing home to safety, Roberts finds that the killer is in his house and is murdered as well. Rushing to Roberts' home, the Angel finds him dead with another blood inked cartoon, leaving the hero to wonder who will be next.

Returning home, The Angel considers the possibility that the killer might have been Bill's brother Jerry, suspecting that he might have killed his own brother to take control of his publication. His thoughts are cut off when Howards, the original writer, calls the Angel in a panic. The Angle rushes to Howards' aid, but falls into a trap. He soon finds himself locked up in a basement with razor blades on the roof along with Jerry and other members of the staff. As it turns out the killer was in reality Howards who himself is a Nazi agent and a former writer for Julius Streicher's Nazi newspapers in Germany, who was sent to America to smash any anti-Nazi material that the US publishes.

He then forces them to come up with a pro Hitler story depicting the Führer as an angel that everyone must love before they are to be killed by the razor blades in the roof. To this end, "Howards" hopes to use their blood to ink multiple copies of the comic they have made. Completing their task under torture, the creative team and the Angel are left to die as the ceiling of razor blades slowly descends on them. Hearing water on the other side of the wall, the Angel uses his chains to pull open a loose brick, causing the room to flood with water. Realizing the water would dilute their blood and make is useless as an ink, Howards stops the trap and fixes the hole and empties the water out of the room.

The Angel breaks free form his bonds and fights off Howards. As he changes into his Angel costume and frees the other creative staff, Howards attempts to escape. The Angel chases after him, deflecting all of the offensive weapons he has at his disposal around his make-shift printing press. Grabbing a tossed bottle of acid, the Angel manages to peg Howards in the butt with it causing the bottle to shatter and the acid to burn through his pants. Seeking relief the Nazi jumps into a vat of water to dilute the acid making him an easy target for the Angel to beat into unconsciousness.

Captured by the authorities and brought before a court, Howards is found guilty of murder and sentenced to death on the electric chair. Having finally snapped, Howards claims that the Angel is dead and presents his comic strip as proof, but when he sees the Angel's trademark shadow across the courtroom he falls into a dead faint.